1. Field of the Invention
The present invention relates to an illumination device and, more particularly, to the shape of a reflector used in a flashlight-emitting device for a camera or the like.
2. Related Art Statement
FIGS. 24 to 32 are views for explaining a conventional flashlight-emitting device for a camera, in which FIG. 24 is a perspective view showing the appearance of a flashlight-emitting device for a camera, FIG. 25 is a cross-sectional view showing the flashlight-emitting device in a direction perpendicular to the axis of a light-emitting tube, FIG. 26 is an upper view of a reflector 2, and FIG. 27 is a front view of an opening portion of the reflector 2.
As shown in FIG. 24, a flashlight-emitting device for a camera is generally constituted by a flashlight discharge tube 1 in which a xenon (Xe) gas or the like is sealed, and a reflector 2 for reflecting light from the flashlight discharge tube 1 in the forward direction. The cross-section perpendicular to the axis direction of the flashlight discharge tube 1, as shown in FIG. 25, is formed to have an elliptical shape or an almost quadratic-curve shape.
As shown in FIG. 24, the side-surface portions of the reflector 2 are constituted by flat plates. As is also apparent from the upper view in FIG. 26, the side-surface portions diverge at a predetermined angle toward the opening portion.
FIGS. 28 to 32 are views for explaining the problems of the conventional flashlight-emitting device for a camera.
FIG. 28 shows a state wherein the shape of an opening portion is changed with respect to the shape of the opening portion of the camera body, and FIGS. 29 and 30 show cross-sectional views of the central portion in FIG. 28. FIG. 29 shows a state wherein the opening portion of the reflector 2 is partially cut away, and FIG. 30 shows a state wherein the opening portion of the reflector 2 is partially masked.
As shown in FIG. 28, when the light-emitting opening portion of the reflector 2 is built in the front surface of the camera body to face an object to be photographed, if the area of the opening portion of the body arranged on the front surface of the camera body is almost equal to the area of the opening portion of the reflector 2, light irradiated on the object is not vignetted (as is the case shown in FIGS. 31 and 32), so that light loss does not occur.
However, when the area of the opening portion of the camera body M is smaller than the area of the opening portion of the reflector 2 as shown in FIG. 28 for scheming or designing convenience, the outer peripheral portion of the reflector 2 is partially cut away as shown in FIG. 29 to make the size of the opening portion of the reflector 2 equal to the size of the opening portion of the camera body, or a predetermined portion of the reflector 2 is covered with a mask 3 to make the sizes of the opening portions equal to each other as shown in FIG. 30. For this reason, loss of light irradiated on the object is large.
More specifically, when the reflector 2 is cut as indicated by a dotted-line portion as shown in FIG. 29, rays of light which would have reflected off the removed surfaces of the reflector are lost. Therefore, a problem of loss of light rays occurs. As shown in FIG. 30, when the reflector 2 is covered, light is reflected and absorbed by the mask 3, which also causes the problem of loss of light rays to occur.
In addition, when the opening portion of the reflector is formed to have a predetermined shape for design, loss of light rays occurs depending on the shape of the opening portion.